组织胚胎学课件 七年制英文医学班专用

1. 组织胚胎学课件七年制英文医学班专用 中国医科大学 基础医学院 组胚—英文教学组

2. Chapter 6 Muscular Tissue

3. 1.General description 1) components: ---cell: muscle fiber-myofiber • elongated thread-liked • Sarcolemma • Sarcoplasm • sarcoplasmic reticulum: SER ---extracellular G.S: CT with BV, LV and N

4. 2) classification According to the structure and function • skeletal muscle: striated, voluntary • cardiac muscle: striated, involuntary • smooth muscle: unstriated, involuntary

5. 2.Skeletal muscle

6. Muscle is an organ, consists of muscle fiber and CT, fixed on bone by tendons CT: • epimysium: DCT • Perimysium • Endomysium • muscle satellite cell: differentiate and proliferate function: supporting, connecting, nourishing and regulating

7. 1)microstructure of skeletal muscle fiber ①long cylindrical 10-100um in diameter,1-40mm long ②multinucleate, nuclei are ovoid, distributed under sarcolemma ③ filled with longitudinal parallel-arranged myofibrils

8. myofibril: • 1-2um in diameter • cross striation: light band -I(isotropic) band, dark band- A(anisotropic) band --A band: M-line, H-band --I band: Z-line

9. * sacromere: a segment of myfibril extending from one Z line to next Z line, which is composed of 1/2 I band, A band and 1/2 I band ,is the smallest structural and functional unit of myofibril

10. 2)Ultrastructure of myofiber ①myofibril: composed of ---thick myofilament: • 1.5 um long, 15nm in diameter • composed of myosin: -rob: in bundles -head: cross bridge- binding site(ATPase activity)

11. ---thin myofilament: • 1um long, 5nm in diameter • composed of: A. actin- spherical monomers of globular-actin arranged in two row and twisted- filamentous actin, each monomer has binding site

12. B.tropomyosin: filamentous protein of two polypeptide chains C. troponin: three sub-units: -Tn T: bind to tropomyosin -Tn C: binds to calcium ions -Tn I: inhibite actin-myosin interaction

13. ②Transverse tubule (T tubule): ---definition: sarcolemma and basement membrane invaginate into sarcoplasm to form a transverse distributed tubular system ---location: A-I junctional part ---function: transfer the information into cytoplasm

14. ③Sarcoplasmic reticulum: ---definition: A longitudinal distributed tubular system formed by smooth endoplasmic reticulum ---structure: • H-A band: longitudinal enclose myofibril-- longitudinal tubule • A-I junction: enlarge to form flattened sac—terminal cisternae * triad: one T-tubule +two terminal cisternae ---function: there are calcium pump proteins (ATPase) on membrane, so it can store and release calcium ions

15. ④Mitochondria, glycogen, lipid droplet

16. 3)Sliding filament hypothesis During the contraction, the A band remained constant in length, whilst the I band and H band both decreased in width, which suggest that the actin filament slide along the myosin toward the M –line.

17. Myoneural junction transfer the impulse from NF to sarcolemme. • The impulse spreads to interior part of cell by T- tubule, then through the triad, impulse is transferred to sarcoplasmic reticulum, the calcium ions are released by sarcoplasmic reticulum. • Calcium bind to Tn C, troponin and tropomyosin change their position and structure, the binding site on actin and myosin is exposed

18. d. Binding site on actin and myosin combine, ATP(adenosine triphosphate) are splitted into ADP(adenosine diphosphate) by ATPase on head of myosin, and energy are release. The energy is provided to band the head in the direction of M-line, and actin filament are pulled toward to M line. e. After contraction, calcium ions in sarcoplasm are withdrawed into sarcoplasmic reticulum. A new ATP molecules bind to the myosin, the actin-myosin separated, troponin-tropomyosin cover the binding site, the myofiber relax.

19. 3.Cardiac muscle

20. 1) Microstructure of cardiac muscle • ①short column in shaped, 100um long,15um in diameter, with branches, the branches associated with each other to form a network • ②1-2 ovoid nuclei, centrally-located • ③striated, but no very clear • ④intercalated disc: junctional part • LM: dark striation across the cardiac fibers

21. 2) Ultrastructure of cardiac muscle similar to skeletal muscle, composed of thick, thin filament and have sarcomere ①myofibril have different diameter, the boundary of myofibril is not very clear

22. ②thansverse tubule are thicker, located at Z-line level ③sarcoplasmic reticulum is not well-developed, form less terminal cisternae * diad: one T-tubule + one terminal cisternae

23. ④intercalated discs step-liked structure • transverse portion: -intermediate junction -desmosome -connection • longitudinal portion: -gap junction -communication

24. ⑤rich in • mitochondria • glycogen • pigment

25. 4. Smooth muscle

26. microstructure of smooth muscle ①elongated, spindle-shaped cells, 8um in diameter, 200( 20-500)um long ②rob-liked or ovoid nucleus ③no striation, no myofibril

27. 2) ultrastructure of smooth muscle ①caveola: sarcolemme invaginate into cytoplasm ② /dense patch: under sarcolemma /dense bodya: in sarcoplasm ③intermediate filament: /composed of desmin /10nm in diameter /connect between dense body

28. ④/thick filament: myosin, 15 nm /thin filament: actin, 5 nm- fixed on dense patch or body • percentage: thick/thin filament=1/12-30 • contractile unit: several thick filament and thin filament aggregate